In your interesting review, you raise in the Discussion that methods of blinding be reported:
"Finally, the results are evolving, and readers are invited to inform us of other methods of blinding not captured in this survey".

Our stratified RCT -corresponding to my doctoral dissertation- evaluated the effects of real or sham spinal manipulation on tonsillitis. We were very careful to make the sham manipulation very similar to the real one, but without thrust; and the verbal and non-verbal interaction of the therapist (not blinded) as similar, brief and aseptic as possible. And the subsequent verbal contact with the patients (to measure the results) was only done by another investigator, blinded. https://www.mdpi.com/2227...

This type of sham manipulation is already described in your article; I am going to explain how we knew that the placebo group was effectively blinded, for two reasons:

1) There was a very important and significant decrease in the number of episodes the following year, compared to the previous year, both in the Control Group (CG) and in the Experimental Group (OMG) (significantly more in the OMG). Despite the fact that the number of annual episodes was increasing in the previous two years. Therefore, the decrease in the subsequent year cannot be attributed to the natural course of the disease, spontaneous remission, or to the conventional treatments that they were receiving. Therefore, the significant decrease in the CG in the following year must obviously be attributed to the placebo effect, achieved with blinding.

2) No patient in the CG reported surprise at not having perceived a cavitation sound, since no patient was told that the protocolized manipulation produced joint sound. Both groups had been told that we were investigating two types of maneuvers to treat tonsillitis.

This effective blinding is consistent with other investigations with sham thoracic manipulations, both sitting and supine, that have been validated [1,2] as methods of sham manipulation in this spinal area, both in healthy subjects [1] and in patients. The comparison of results of a group with real spinal manipulation, with respect to another with simulated manipulation, has been successfully carried out in randomized clinical trials. Our methodology is consistent with the recommendations of the Guide for Reporting Interventions in Spinal Manipulative Therapy (CIRCLe SMT) [3], an international consensus document published in 2017, which details how to record the methodology of this type of study.
The “sham manipulation”, applying a “light touch methodology”, was validated by the Institutional Review Board of North Texas Health Science Center [4,5] and used increasingly in clinical trials with spinal manipulation [6,7]. It has also been used in clinical trials with thoracic spinal manipulation, where it has been specifically validated as just discussed [1,2].


Regards,
Dr. Agustín Luceño PT, PhD

[1] Michener LA, Kardouni JR, Lopes Albers AD, Ely JM. Development of a sham comparator for thoracic spinal manipulative therapy for use with shoulder disorders. Man Ther. 2013;18(1):60-4.
[2] Michener LA, Kardouni JR, Sousa CO, Ely JM. Validation of a sham comparator for thoracic spinal manipulation in patients with shoulder pain. Man Ther. 2015;20(1):171-5.
[3] Groeneweg R, Rubinstein SM, Oostendorp RAB, Ostelo RWJG, van Tulder MW. Guideline for Reporting Interventions on Spinal Manipulative Therapy: Consensus on Interventions Reporting Criteria List for Spinal Manipulative Therapy (CIRCLe SMT). J Manipulative Physiol Ther. 2017;40(2):61-70.
[4] Licciardone JC, Minotti DE, Gatchel RJ, Kearns CM, Singh KP. Osteopathic manual treatment and ultrasound therapy for chronic low back pain: A randomized controlled trial. Ann Fam Med. 2013;11(2):122-9.
[5] Ditcharles S, Yiou E, Delafontaine A, Hamaoui A. Short-Term Effects of Thoracic Spine Manipulation on the Biomechanical Organisation of Gait Initiation: A Randomized Pilot Study. Front Hum Neurosci. 2017;11:343.
[6] Vernon H, Triano J, Ross K, Soave D, Tran S. Validation of a novel sham cervical manipulation procedure. Clin Chiropr. 2011;14(4):177.
[7] Chaibi A, Šaltytė Benth J, Bjørn Russell M. Validation of Placebo in a Manual Therapy Randomized Controlled Trial. Sci Rep. 2015;5:11774.